The invention relates to a surgical instrument with an energy-driven operating device, an energy storage device as well as a control device for operating the operating device as required and supplying it with energy from the energy storage device.
Instruments of this type are known with an operating device which is driven electrically or pneumatically. Accumulators or batteries or rather gas cartridges serve as energy storage devices.
The energy capacity is necessarily limited in the case of such instruments, with the risk that operating processes can no longer be finished when the charge capacity is exhausted.
This is a problem, in particular, in the case of operations which relate to the central nervous system when the instruments are used to remove, for example, bones or tissue material from the patient with a considerable use of force, for example with so-called bone punches.
In the case of bone punches, forces of approximately 700 to approximately 750 N occur when bone material is removed. If the supply of energy fails while a punch cutter is being transferred from an operating position into an end position, in which the operating process is brought to an end, it remains on the bone and can become locked in position. The problem for the surgeon is then that the bone punch cannot be released from the patient and replaced by another instrument ready for use.
Other fields of use relate to clip appliers for, for example, vessel clips, anastomosis clips as well as aneurysm clips. Furthermore, the fields of use relate to so-called rongeurs or also other cutting instruments which must reliably remove body tissue or bone material in a manner similar to the punches specified above.
It is important for all these fields of use that an operating cycle can be run through such that, afterwards, the instrument is again in a defined starting position or rest position.
On the other hand, it is of significance in the case of the surgical instruments of the present invention that size and weight of the instrument are balanced with a view to ergonomic aspects. The space for accommodating the energy storage device is considerably restricted as a result. A generous dimensioning of the energy storage device from the point of view of safety cannot be realized for this reason alone. A permanent connection to an external energy source is also not desirable from an ergonomic point of view.
In many cases, operations do, however, require a supply of energy which would necessitate too large a volume and weight for one single energy storage device. This situation, in which the energy storage device is exhausted during an operation once or several times, is, therefore, foreseeable in many cases. In such a case, care has to be taken for the reasons specified that the instrument does not remain in an undefined operating state when the energy storage device is exhausted since this would entail a risk for the patient being treated and, in addition, hinder the work of the surgeon.
It has so far been suggested in the state of the art to dimension the energy storage device as far as possible such that all the operating processes can be completely finished with the charge capacity available. This can be brought about in the case of so-called clip appliers relatively simply in that the capacity of the clip magazine is reduced so that all the clips in the magazine can be applied before the energy storage device is exhausted.
In the case of instruments, with which the energy requirements per operating step cannot be predetermined so easily and precisely, it has been suggested in EP 1 884 204 A2 to use a counter for monitoring the supply of energy and to stop use of the instrument when it is likely from the number of operating processes that the energy storage device is almost exhausted.
Operation without any risk can be realized with this manner of proceeding only when the number of permissible operating processes is selected such that use of the instrument is stopped long before exhaustion of the energy storage device is reached.
A similar measure is also suggested in U.S. Pat. No. 6,619,529 B1 for a surgical clip applier, with which a counter likewise records the operating processes and use of the instrument is stopped after a predetermined number of operating processes, i.e. clips applied.
These concepts are unsatisfactory, in particular, for instruments which are more complex from an energy point of view since the supply of energy from the energy storage device can be used only very incompletely on account of the different energy requirements per operating process or, in another case, the risk is still present of the instrument no longer being supplied with the necessary energy while an operating process is being carried out, with the consequences described above.
The object of the present invention is to further develop a surgical instrument of the type described at the outset such that an optimum utilization of the capacity of the energy storage device is achieved without any risk for the surgeon or the patient, in particular in view of the different energy requirements of the individual operating processes.